Ruthenium(II)−Bipyridine/NanoC 3 N 4 Hybrids: Tunable Photochemical Properties by Using Exchangeable Alkali Metal Cations

A series of nanoporous carbon nitrides that contained a range of alkali metal cations (M@nanoC 3 N 4 : M=Li + , Na + , K + , Rb + , and Cs + ) have been successfully synthesized from as‐synthesized g‐C 3 N 4 by delamination with concentrated sulfuric acid, followed by neutralization with aqueous solutions of the corresponding alkali metal hydroxides. Tris(2,2′‐bipyridine)ruthenium(II) complexes, [Ru(bpy) 3 ] 2+ , were grafted onto the carbon nitrides in an effort to explore the physicochemical properties of the deposited [Ru(bpy) 3 ] 2+ , as well as its photocatalytic activity in the aerobic photooxidation of phenylboronic acid and H 2 production from aqueous media in the presence of a Pt co‐catalyst under visible‐light irradiation. Highly porous nanoC 3 N 4 could significantly enhance photocatalytic activity, because of its high surface area, owing to its unique porous structure. More interestingly, the photoluminescence intensities of [Ru(bpy) 3 ] 2+ complexes that were associated with M@nanoC 3 N 4 increased in the presence of lighter alkali metal cations, which correlated with increased photocatalytic activities for both reactions. This study demonstrates that M@nanoC 3 N 4 are fascinating supports, in which the local environment of an immobilized metal complex can be precisely controlled by varying the alkali metal cation from Li + to Cs + .